We have established the fact that respiratory heat loss, or airway cooling, is responsible for initiating bronchospasm induced by exercise and body cooling. We are currently searching for the link between airway cooling and bronchospasm. We used atropine to investigate a possible vegal reflex. Our preliminary results indicate that inhaled atropine aerosol does not reach all airways where cholinergic innervations are present. Increased doses of inhaled atropine do not increase the effect of cholinergic receptor blockade. These results suggest that the reason exercise-induced asthma can not be completely blocked by inhaled atropine is incomplete blockade of cholinergic receptors.